Fermentation of inoculated medium with Xanthomonas organisms for 36 to 72 hours under aerobatic conditions results in the formation of xanthan gum which is separated from other components of the medium by precipitation with acetone or methanol in a known manner. Because of the time required to ferment each batch, the low biopolymer content of the fermented medium and the processing steps required for recovery and purification of the product, xanthan is relatively expensive. Earlier work has indicated that heteropolysaccharides produced by the action of Xanthomonas bacteria on carbohydrate media have potential application as film-forming agents, as thickeners, for body-building agents, and edible products, cosmetic preparations, pharmaceutical vehicles, oil field drilling fluids, fracturing liquid, and emulsifying, stabilizing and sizing agents. Heteropolysaccharides, particularly xanthan gum, have significant potential as mobility control agents in micellar polymer flooding. Xanthan gum has excellent viscosifying properties at low concentration. It is resistant to shear degradation and exhibits only minimal losses in viscosity as a function of temperature, pH, and ionic strength. For these reasons, it is an attractive alternative to synthetic polyacrylamides for enhanced oil recovery operations. However, in order for xanthan gum to be used in enhanced oil recovery operations as a mobility control agent, the cost must be sufficiently low to make such operations economical. It has been shown that the economics of xanthan gum fermentation are sensitive, at least in part, to the yield of xanthan produced in relationship to the amount of glucose consumed. Therefore, any process improvements which enhance xanthan yield will improve the overall economics. For example, in a normal fermentation process increasing the xanthan yield from 60% to 80% can lower the per pound price of xanthan by as much as 10%.
The most pertinent prior art of which I am aware includes the following:
1. P. Rogovin, et al., 1970, Continuous Fermentation to Produce Xanthan Biopolymer:Laboratory Investigation, Biotechnology and Bioengineering, XII, pp. 75-83.
2. G. P. Lindblom, et al., U.S. Pat. No. 3,328,262, "Heteropolysaccharide Fermentation Process".